Irish orthography is the set of conventions used to write Irish. A spelling reform in the mid-20th century led to An Caighdeán Oifigiúil, the modern standard written form used by the Government of Ireland, which regulates both spelling and grammar. The reform removed inter-dialectal silent letters, simplified some letter sequences, and modernised archaic spellings to reflect modern pronunciation, but it also removed letters pronounced in some dialects but not in others. Irish spelling represents all Irish dialects to a high degree despite their considerable phonological variation, e.g. crann ("tree") is read in Mayo and Ulster, in Galway, or in Munster. Some words may have dialectal pronunciations not reflected by their standard spelling, and they sometimes have distinct dialectal spellings to reflect this.

Alphabet

Latin script has been the writing system used to write Irish since the 5th century, when it replaced Ogham, which was used to write Primitive Irish and Old Irish. Prior to the mid-20th century, Gaelic type (cló Gaelach) was the main typeface used to write Irish; now, it is usually replaced by Roman type (cló Rómhánach). The use of Ogham and Gaelic type today is restricted to decorative or self-consciously traditional contexts. The dot above a lenited letter in Gaelic type is usually replaced by a following in Roman type (e.g. → ).

Letters and letter names

The traditional Irish alphabet (aibítir) consists of 18 letters:. It does not contain, although they are used in scientific terminology and modern loanwords of foreign origin. occurs in a small number of (mainly onomatopoeic) native words (e.g. vácarnach "to quack" and vrác "caw") and colloquialisms (e.g. víog for bíog "chirp" and vís for bís "screw"). , when not prefixed to a word initial vowel or after a consonant to show lenition, primarily occurs word initially in loanwords, e.g. hata "hat". is the only letter not listed by Ó Dónaill. Vowels may be accented with an acute accent (see below). Accented letters are considered variants of their unaccented equivalent, and they follow their unaccented equivalents in dictionaries (i.e. a, á…abhac, ábhacht, abhaile...). English letter names are generally used in both colloquial and formal speech but there are modern Irish letter names (based on the original Latin names), similar to other languages that use a Latin script alphabet. Tree names were historically used to name the letters. Tradition taught that they all derived from the names of Ogham letters, though it is now known that only some of the earliest were named after trees.

Grapheme to phoneme correspondence

In grapheme to phoneme correspondence tables on this page: See Irish phonology for an explanation of the symbols used and Irish initial mutations for an explanation of eclipsis and lenition.

Consonants

Consonants are generally "broad" (velarised) when beside and "slender" (palatalised) when beside. Irish orthography does not allow consonant letters or digraphs to be doubled (except in ), in compound words which would result in doubled consonants they are broken up by a hyphen (see below).

Vowels

Vowel sequences are common in Irish spelling due to the "caol le caol agus leathan le leathan" ("slender with slender and broad with broad") rule, i.e. that the vowels on either side of any consonant (or consonant cluster) must be both slender or both broad, to unambiguously determine if the consonant(s) are broad or slender. An apparent exception is, which is followed by a broad consonant despite the. The pronunciation of vowels in Irish is mostly predictable from the following rules:

Followed by

When followed by, a short vowel usually forms a diphthong or lengthens. For, see - in exceptions in verb forms.

Epenthesis

After a short vowel, an unwritten epenthetic gets inserted between + (as well as, when derived from devoiced ), when within a morpheme boundary, e.g. gorm "blue", dearg "red", dorcha "dark", ainm "name", deilgneach "prickly, thorny"’ leanbh "child", airgead "silver, money". The main exception to this is which is mainly used for or. Epenthesis does not occur after long vowels and diphthongs, e.g. téarma "term" or dualgas "duty", or across morpheme boundaries (i.e. after prefixes and in compound words), e.g. garmhac "grandson" (from gar- "close, near" + mac "son"), an-chiúin "very quiet" (from an- "very" + ciúin "quiet"), carrbhealach "carriageway, roadway" (from carr "car" + bealach "way, road"). In Munster, epenthesis also occurs across morpheme boundaries, when follow (after any vowel) or (after short vowels), and when follows.

Exceptions in verb forms

In verb forms, some letters and letter combinations are pronounced differently from elsewhere.

Diacritics

An Caighdeán Oifigiúil currently uses one diacritic, the acute accent, though traditionally a second was used, the overdot. If diacritics are unavailable, e.g. on a computer using ASCII, the overdot is replaced by a following, e.g. Ḃí sé → Bhí sé "He/It was" and there is no standard for replacing an acute accent, though sometimes it is indicated by a following slash, e.g. fírinne → fi/rinne "truth". The acute accent (agúid or (síneadh) fada "long (sign)") is used to indicate a long vowel, as in bád "boat". However, there are other conventions to indicate a long vowel, such as: The overdot (ponc séimhithe "dot of lenition") was traditionally used to indicate lenition, though An Caighdeán exclusively uses a following for this purpose. In Old Irish, the overdot was only used for, while the following was used for and the lenition of other letters was not indicated. Later the two methods were used in parallel to represent lenition of any consonant (except ) until the standard practice became to use the overdot in Gaelic type and the following in Roman type. Thus the dotted letters (litreacha buailte "struck letters") are equivalent to letters followed by a, i.e.. Lowercase has no tittle in Gaelic type, and road signs in the Republic of Ireland. However, as printed and electronic material like books, newspapers and web pages use Roman type almost invariably, the tittle is generally shown. Irish does not graphemically distinguish I|dotted i and dotless ı, i.e. they are not different letters as they are in, e.g. Turkish and Azeri.

Punctuation

Irish punctuation is similar to English. An apparent exception is the Tironian et (agus) which abbreviates the word agus "and", like the ampersand abbreviates "and" in English. It is generally substituted by a 7|seven in texts. A hyphen (fleiscín) is used in Irish after when prefixed to a masculine vowel-initial word as an initial mutation, e.g. an t-arán "the bread", a n-iníon "their daughter". However, it is omitted when the vowel is capitalised, e.g. an tAlbanach "the Scotsman", Ár nAthair "Our Father". No hyphen is used when is prefixed to a vowel-initial word, e.g. a hiníon "her daughter". A hyphen is also used in compound words under certain circumstances: An apostrophe (uaschamóg) is used to indicate an omitted vowel in the following cases:

Capitalisation

Capitalisation rules are similar to English. However, a prefixed letter remains in lowercase when the base initial is capitalised (an tSín "China"). For text written in all caps, the prefixed letter is kept in lowercase, or small caps (STAIR NA ÉIREANN "THE HISTORY OF IRELAND"). An initial capital is used for:

Abbreviations

Most Irish abbreviations are straightforward, e.g. leathanach → lch. ("page → p.") and mar shampla → m.sh. ("exempli gratia (for example) → e.g."), but two that require explanation are: is é sin → .i. ("that is → i.e.") and agus araile → ⁊rl./srl. ("et cetera (and so forth) → &c./etc."). Like in English, follows an ordinal numeral, e.g. Is é Lá Fheile Phádraig an 17ú lá den Márta "St. Patrick's day is the 17th [day] of March".

Spelling reform

The literary Classical Irish which survived till the 17th century was archaic; the first attempt at simplification was not until 1639. The spelling represented a dialect continuum including distinctions lost in all surviving dialects by the Gaelic revival of the late 19th century. The idea of a spelling reform, linked to the use of Roman or Gaelic type, was controversial in the early decades of the 20th century. The Irish Texts Society's 1904 Irish-English dictionary by Patrick S. Dinneen used traditional spellings. After the creation of the Irish Free State in 1922, all Acts of the Oireachtas were translated into Irish, initially using Dinneen's spellings, with a list of simplifications accumulating over the years. When Éamon de Valera became President of the Executive Council after the 1932 election, policy reverted to older spellings, which were used in the enrolled text of the 1937 Constitution. In 1941, de Valera decided to publish a "popular edition" of the Constitution with simplified spelling and established a committee of experts, which failed to agree on recommendations. Instead, the Oireachtas' own translation service prepared a booklet, Litriú na Gaeilge: Lámhleabhar an Chaighdeáin Oifigiúil, published in 1945. Some pre-reform spellings criticised by T. F. O'Rahilly and their modern forms include: beirbhiughadh → beiriú, imthighthe → imithe, faghbháil → fáil, urradhas → urrús, filidheacht → filíocht. The booklet was expanded in 1947, and republished as An Caighdeán Oifigiúil "The Official Standard" in 1958, combined with the standard grammar of 1953. It attracted initial criticism as unhistorical and artificial; some spellings fail to represent the pronunciation of some dialects, while others preserve letters unpronounced in any dialect. Its status was reinforced by use in the civil service and as a guide for Tomás de Bhaldraithe's 1959 English–Irish dictionary and Niall Ó Dónaill's 1977 Irish–English dictionary. A review of the written standard, including spelling, was announced in 2010, aiming to improve "simplicity, internal consistency, and logic". The result was the 2017 update of An Caighdeán Oifigiúil.